1. Field of the Invention
The present invention concerns a medical apparatus for implementation of operative procedures on a patient with image acquisition device and position determination device combined in the medical apparatus.
2. Description of the Prior Art
During operative procedures on a patient, the control of surgical instruments (such as, for example, laparoscopes, endoscopes, needles, etc.) often ensues by means of various image-supported methods.
In the simplest case, purely image-supported positionings of medical instruments are implemented, meaning that the instrument position is directly visible and can be tracked in the image. Examples of this are the needle guidance (for example for biopsies or RF ablations) by means of ultrasound, CT fluoroscopy or x-ray fluoroscopy. These methods are characterized by real-time capability and are standards today in specific application fields.
Another widespread method is the use of surgical navigation based on preoperative images. In this case the positioning of the instruments is implemented with the assistance of navigation systems on the basis of image data that were acquired before the actual operation on the patient. The image data are normally based on CT or MR images; but, SPECT (Single Photon Emission Computed Tomography) or PET (Positron Emission Tomography) images are also increasingly used. An example of the implementation of methods based on preoperative images the use of is robotics in orthopedics or neurosurgery. Operations on the knee and on the hip are also examples of a robot-supported operative procedure. Conventionally, such procedures are implemented exclusively using CT x-ray images of the region to be operated upon that are acquired before the operative procedure.
Other procedures, however, which can lead to a position change or position changes, require continuous monitoring images during the procedure in order to ensure a reliable positioning of the medical instruments, and therewith a safe implementation of the operation. In this case navigation and imaging are combined during the procedure, with new (updated) images of the patient being acquired as needed during the operation (for example after bone reduction (realignment of a fractured bone), after tissue removal (extraction) and after physical changes in position) and are provided to the navigation so that this can always be based on current image data. The use of such a medical method to support operative procedures on a patient is also useful when the surgeon is blocked from the viewing of the working end of a medical instrument directed by him or her and penetrating into the body of the patient and/or when a correlation between a position and shape of a body part or an organ shown in an image acquired beforehand, and the actual position and shape of the body part or organ is not available during the operation. Such an absence of correlation can occur either because the position of the patient during the operation on a patient bed does not precisely correspond to the position of the patient in the preoperative image acquisition or because, for example, deformations of body parts, deformations of organs or variations of organ positions occur due to natural movements (for example heartbeat, respiration, peristalsis).
The navigation system thus serves for the precise determination of the spatial coordinates, i.e. the position and orientation of the instrument in space or at an operation site. The image of the instrument should be mixed as accurately as possible into an image acquired with the image acquisition system. Multiple camera systems (for example CCD (charge coupled device) cameras) are often used as detection sensors in the position determination device of the navigation system, but other sensors that operate on electromagnetic principles are also conceivable. Ultrasound methods, although generally conceivable, rarely play a role any more today due to their disadvantages with regard to reflections and temperature dependency. The navigation systems, in particular the position determination device with its detection sensors, normally can be freely positioned in the operating room. In any case, however, the position determination device is designed separate from the image acquisition device. This must in many cases be perceived as a disadvantage since there must be good compatibility between the image acquisition device and the position determination device. For example, in order to enable such a navigation-directed procedure it is necessary to produce a mathematical relation in the form of a coordinate transformation between the coordinate system of the image information of the patient, or the coordinate system of the reconstructed volume of the patient, and the coordinate system of the sensors of the position determination device acquiring the medical instruments.
A device for determination of a coordinate transformation for navigation-directed procedures is known for a C-arm x-ray apparatus from DE 199 17 867. The known device has an adapter with markers that can be detected by a navigation system as well as a reference structure with x-ray-positive markings. A coordinate transformation between a coordinate system associated with the navigation system and a coordinate system associated with the x-ray image can be produced using the reference structure and the adapter. Sometimes identifiers (artificial markers) that are artificially arranged on the patient, or anatomically-dependent markers (such as, for example, distinctive bone structures) are used as markers. The markers must therefore normally be approached individually and in the correct order with the instrument in order to be able to determine the coordinate transformation between the two coordinate systems.
DE 102 10 287 provides a method for marker-less registration for navigation-directed procedures. According to this method, coordinate systems are assigned to an x-ray calibration phantom and the mounting of the x-ray apparatus. Coordinate transformations between the two coordinate systems then can be produced with acquisitions and evaluations of 2-D projections of the x-ray calibration phantom.
In both aforementioned documents, the position determination device of the navigation system and the image acquisition device are separate from one another; the imaging x-ray apparatuses are mobile. Each relative movement between the navigation system and the x-ray apparatus either involves a new calibration or is taken into account by the use of reference markers that, for example, are mounted on the operating table.
Freely-positionable position determination devices (thus essentially the sensors for navigation systems) are mounted in the operating room, normally at some distance from the operation region. This has the disadvantage that the sensitive volume (thus the acquired region) is relatively large, which in turn entails disadvantages in the resolution of the sensors. Furthermore, other components (such as, for example, markers) to be acquired by the position determination device must be designed correspondingly large in order to be reliably detected. In some cases it can even lead to occlusion (blocking) of sensors, for example by the treating operation team, or at least to a certain limitation of their freedom of movement.
A medical system with an imaging system and a navigation system is described in DE 199 51 503, wherein navigation system is “informed” of the usage of a movable C-arm x-ray apparatus. This movable C-arm x-ray apparatus is to be brought to a patient simply and quickly as needed for the purpose of the necessary image acquisitions for a navigation-directed procedure and can be removed again in the event that it is no longer required. The navigation system itself is, as noted above, arranged separately in the operating room with its position determination devices. The aforementioned disadvantages with regard to calibration of imaging hardware and the navigation hardware that also exist.